While the Queensland Senator technically remains leader of the Nationals in the Senate until after the election, it's not expected that the 43rd Parliament will actually sit again before polling day.

The Nationals will vote to elect their new Senate leader after the election, and the ABC understands there is more than one senator interested in the role.

Senator Joyce appeared to give his blessing to his deputy, NSW Senator Fiona Nash; handing her his boots, mounted on a plaque, and naming her 'Custodian of the Boots' at a press call in Parliament House today.

Senator Joyce is the Nationals candidate for the lower house NSW seat of New England, and is widely tipped to succeed following this week's announcement that the incumbent, independent Tony Windsor, is retiring.

His well-worn black boots have now been mounted onto a plaque, which will record the names of all the Nationals' Senate leaders.

Senator Joyce says the boots represent what the National Party's all about.

"First of all, they're Australian made," he said, to the chuckles of his colleagues.

"They represent that you're down here to work the corridors, to lobby, the capacity to do the hard legwork to get around and make sure that the people you're here to serve feel justified in casting their vote in your direction."

Senator Nash used the occasion to again call on the new Treasurer, Chris Bowen, to reject any application from American agribusiness Archer Daniels Midland (ADM) to buy the Australian grain giant GrainCorp.

"This [sale] is not in the national interest, and it's not in grain growers' interest," she said.

GrainCorp controls the majority of grain transport, storage and export infrastructure along Australia's east coast.

The ACCC yesterday said it would not block the sale, which still requires the approval of the Foreign Investment Review Board and, ultimately, the Treasurer.

"GrainCorp has around 280 receival sites, they hold virtually all the ports [on the east coast]. We have a virtual monopoly which is potentially going into the hands of Archer Daniels Midland, an enormous grain giant and multinational.

"This company operates in 140 nations around the globe. Australia's eastern seaboard logistics system will become a tiny cog in that giant multinational empire.

"I'm calling on the Treasurer to reject any approval from the Foreign Investment Review Board for this takeover to go ahead."